“Our cleaner members have voted decisively for action on GWR. RMT will not stand by while they are mercilessly exploited by privateers, while rail companies fill their coffers as fares soar through the roof," said Mick Cash the general secretary of the RMT.

The news comes as south-east Britain is preparing for double-whammy of strike action.

RMT members have abstaining from work on a regular basis for a large proportion of 2016 as part of an ongoing dispute with Southern rail over who owns the train doors – the driver or a guard.

Drivers union Aslef last week announced a ban on working overtime – a vitally important element of flexibility on the nation's rail network – and themselves have walkouts planned for this week and next. This week's action by Aslef will mean Southern rail will not be able to run any trains.

In relation to the GWR dispute, the RMT balloted 189 members and had a 58 per cent turnout. 98 per cent voted for strike action and exactly the same percentage voted for action short of a strike in the ballot.

City A.M. has approached GWR for comment but has not received a response at the time of writing.